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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Experimental evaluation of two premixing-prevaporizing fuel injection concepts for a gas turbine catalytic combustor

A premixing-prevaporizing fuel system for a gas turbine catalytic combustor has been developed and evaluated. Spatial fuel distribution and degree of vaporization were measured at inlet temperatures up to 800 K and fuel-air ratios of 0.01 and 0.025. The test pressure was 0.5 MPa; velocity was 20 m/sec. Both a multiple-jet cross-stream injector and a splash-groove injector with a 30 deg air swirler exhibited a uniform fuel distribution and a high degree of vaporization with little total pressure drop. Fuel oxidation reactions were observed at the 800 K inlet air temperature, indicating that a different design concept is necessary for application with an automotive gas turbine.

Tacina, R.↗
NASA NTRS1975

Examination of the costs, benefits and enery conservation aspects of the NASA aircraft fuel conservation technology program

The costs and benefits of the NASA Aircraft Fuel Conservation Technology Program are discussed. Consideration is given to a present worth analysis of the planned program expenditures, an examination of the fuel savings to be obtained by the year 2005 and the worth of this fuel savings relative to the investment required, a comparison of the program funding with that planned by other Federal agencies for energy conservation, an examination of the private industry aeronautical research and technology financial posture for the period FY 76 - FY 85, and an assessment of the potential impacts on air and noise pollution. To aid in this analysis, a computerized fleet mix forecasting model was developed. This model enables the estimation of fuel consumption and present worth of fuel expenditures for selected commerical aircraft fleet mix scenarios.

Source record↗
NASA NTRS1977

Influence of fuel temperature on supersonic mixing and combustion of hydrogen

Results are presented from an experimental investigation of the influence of fuel stagnation temperature on the mixing and reaction of hydrogen injected transverse to a supersonic flow in a duct. The hydrogen fuel was injected stoichiometrically at stagnation temperatures of 300 K and 800 K from a row of five circular orifices in the duct wall. Detailed measurements in the flow at the duct exit are used to determine the overall amount of mixing accomplished at each of three test conditions. Static pressure distributions are used with duct wall temperatures and heat flux in a one-dimensional analysis to deduce the fraction of fuel reacted along the duct. Results from the one-dimensional analyses of the tests with hot fuel indicated slightly more fuel reacted at the exit; however, differences in the accomplished mixing obtained from integrations of exit surveys were small.

Rogers, R. C.↗
NASA NTRS1977

The influence of droplet evaporation on fuel-air mixing rate in a burner

Experiments involving combustion of a variety of hydrocarbon fuels in a simple atmospheric pressure burner were used to evaluate the role of droplet evaporation in the fuel/air mixing process in liquid fuel spray flames. Both air-assist atomization and pressure atomization processes were studied; fuel/air mixing rates were determined on the basis of cross-section average oxygen concentrations for stoichiometric overall operation. In general, it is concluded that droplets act as point sources of fuel vapor until evaporation, when the fuel jet length scale may become important in determining nonuniformities of the fuel vapor concentration. In addition, air-assist atomizers are found to have short droplet evaporation times with respect to the duration of the fuel/air mixing process, while for the pressure jet atomizer the characteristic evaporation and mixing times are similar.

Komiyama, K.↗
NASA NTRS1977

Fuel system protection

The hazardous nature of most fuels and the potential for catastrophe if ignition should occur was investigated in regard to the design of adequate lightning protection for aircraft fuel systems. Typical aircraft fuel flammability characteristics and possible ways to control fuel flammability and ignition were reviewed. Guidelines for effective protection of fuel systems were delineated.

Franklin A Fisher↗
NASA NTRS1977

Alternative fuels

Potential problems related to the use of alternative aviation turbine fuels are discussed and both ongoing and required research into these fuels is described. This discussion is limited to aviation turbine fuels composed of liquid hydrocarbons. The advantages and disadvantages of the various solutions to the problems are summarized. The first solution is to continue to develop the necessary technology at the refinery to produce specification jet fuels regardless of the crude source. The second solution is to minimize energy consumption at the refinery and keep fuel costs down by relaxing specifications.

Grobman, J. S.↗
NASA NTRS1977

Alternative aircraft fuels

The efficient utilization of fossil fuels by future jet aircraft may necessitate the broadening of current aviation turbine fuel specifications. The most significant changes in specifications would be an increased aromatics content and a higher final boiling point in order to minimize refinery energy consumption and costs. These changes would increase the freezing point and might lower the thermal stability of the fuel, and could cause increased pollutant emissions, increased combustor liner temperatures, and poorer ignition characteristics. The effects that broadened specification fuels may have on present-day jet aircraft and engine components and the technology required to use fuels with broadened specifications are discussed.

Longwell, J. P.↗
NASA NTRS1978

Photographic characterization of spark-ignition engine fuel injectors

Manifold port fuel injectors suitable for use in general aviation spark-ignition engines were evaluated qualitatively on the basis of fuel spray characteristics. Photographs were taken at various fuel flow rates or pressure levels. Mechanically and electronically operated pintle injectors generally produced the most atomization. The plain-orifice injectors used on most fuel-injected general aviation engines did not atomize the fuel when sprayed into quiescent air.

Evanich, P. L.↗
NASA NTRS1978

Combustion of hydrogen in a two-dimensional duct with step fuel injectors

An investigation of the combustion of hydrogen perpendicularly injected from step fuel injectors into a Mach 2.72, 2100 K vitiated test gas was conducted. The model simulated the flow between the center and side struts of an integrated scramjet module at Mach 7 flight and an altitude of 29 km. Parametric variation included equivalence ratio, fuel dynamic pressure ratio, and area distribution of the model. The overall area ratio of the model was held constant at 2.87. The data analysis indicated that no measurable improvement in mixing or combustion efficiency was obtained by varying the fuel dynamic pressure ratio from 0.79 to 2.45. Computations indicated approximately 80 percent of the fuel was mixed so that it could react; however, only approximately 50 percent of the mixed fuel actually reacted in two test configurations, and 74 percent in later tests where less area expansion of the flow occurred.

Eggers, J. M.↗
NASA NTRS1978

Evaluation of the SSRCT engine with a hydrazine as a fuel, phase 1

The performance parameters for the space shuttle reaction control thruster (SSRCT) when the fuel is changed from monomethylhydrazine to hydrazine were predicted. Potential problems are higher chamber wall temperature during steady state operation and explosive events during pulse mode operation. Solutions to the problems are suggested. To conduct the analysis, a more realistic film cooling model was devised which considers that hydrazine based fuels are reactive when used as a film coolant on the walls of the combustion chamber. Hydrazine based fuels can decompose exothermally as a monopropellant and also enter into bipropellant reactions with any excess oxidizer in the combustion chamber. It is concluded that the conversion of the thruster from MMH to hydrazine fuel is feasible but that a number of changes would be required to achieve the same safety margins as the monomethylhydrazine-fueled thruster.

Minton, S. J.↗
NASA NTRS1978

Characteristics and combustion of future hydrocarbon fuels

As the world supply of petroleum crude oil is being depleted, the supply of high-quality crude oil is also dwindling. This dwindling supply is beginning to manifest itself in the form of crude oils containing higher percentages of aromatic compounds, sulphur, nitrogen, and trace constituents. The result of this trend is described and the change in important crude oil characteristics, as related to aircraft fuels, is discussed. As available petroleum is further depleted, the use of synthetic crude oils (those derived from coal and oil shale) may be required. The principal properties of these syncrudes and the fuels that can be derived from them are described. In addition to the changes in the supply of crude oil, increasing competition for middle-distillate fuels may require that specifications be broadened in future fuels. The impact that the resultant potential changes in fuel properties may have on combustion and thermal stability characteristics is illustrated and discussed in terms of ignition, soot formation, carbon deposition flame radiation, and emissions.

Rudey, R. A.↗
NASA NTRS1978

Solid Polymer Electrolyte (SPE) fuel cell technology program

Many previously demonstrated improved fuel cell features were consolidated to (1) obtain a better understanding of the observed characteristics of the operating laboratory-sized cells; (2) evaluate appropriate improved fuel cell features in 0.7 sq ft cell hardware; and (3) study the resultant fuel cell capability and determine its impact on various potential fuel cell space missions. The observed performance characteristics of the fuel cell at high temperatures and high current densities were matched with a theoretical model based on the change in Gibbs free energy voltage with respect to temperature and internal resistance change with current density. Excellent agreement between the observed and model performance was obtained. The observed performance decay with operational time on cells with very low noble metal loadings (0.05 mg/sq cm) were shown to be related to loss in surface area. Cells with the baseline amount of noble catalyst electrode loading demonstrated over 40,000 hours of stable performance.

Source record↗
NASA NTRS1977

Hydrogen fueled subsonic aircraft - A prospective

The performance characteristics of hydrogen-fueled subsonic transport aircraft are compared with those of aircraft using conventional aviation kerosene. Results of the Cryogenically Fueled Aircraft Technology Program sponsored by NASA indicate that liquid hydrogen may be particularly efficient for subsonic transport craft when ranges of 4000 km or more are involved; however, development of advanced cryogenic tanks for liquid hydrogen fuel is required. The NASA-sponsored program also found no major technical obstacles for international airports converting the liquid hydrogen fueling systems. Resource utilization efficiency and fuel production costs for hydrogen produced by coal gasification or for liquid methane or synthetic aviation kerosene are also assessed.

Witcofski, R. D.↗
NASA NTRS1978

Fuel saving potential of Mach 0.8 twin engine prop-fan transports

The fuel saving and economic potentials of the prop-fan high-speed propeller concept have been evaluated for twin-engine commercial transport airplanes designed for 3333.6 km range, 180 passengers, and Mach 0.8 cruise. A fuel saving of 9.7% at the design range was estimated for a prop-fan aircraft having wing-mounted engines, while a 5.8% saving was estimated for a design having the engines mounted on the aft body. The fuel savings and cost were found to be sensitive to the propeller noise level and to aerodynamic drag effects due to wing-slipstream interaction. Uncertainties in these effects could change the fuel savings as much as plus or minus 50%. A modest improvement in direct operating cost was estimated for the wing-mounted prop-fan at current fuel prices.

Davenport, F. J.↗
NASA NTRS1979

Design and evaluation of aircraft heat source systems for use with high-freezing point fuels

The objectives were the design, performance and economic analyses of practical aircraft fuel heating systems that would permit the use of high freezing-point fuels on long-range aircraft. Two hypothetical hydrocarbon fuels with freezing points of -29 C and -18 C were used to represent the variation from current day jet fuels. A Boeing 747-200 with JT9D-7/7A engines was used as the baseline aircraft. A 9300 Km mission was used as the mission length from which the heat requirements to maintain the fuel above its freezing point was based.

Pasion, A. J.↗
NASA NTRS1979

Modeling of premixing-prevaporizing fuel-air mixing passages

The development of a computer program for the analytical prediction of the distribution of liquid and vapor fuel in the premixing-prevaporizing passage by the direct injection method is described. The technical approach adopted for this program is to separate the problem into three parts each with its own computer code. These three parts are: calculation of the two-dimensional or axisymmetric air flow; calculation of the three-dimensional fuel droplet evaporation; and calculation of the fuel vapor diffusion. This method of approach is justified because premixing passages operate at lean equivalence ratios. Hence, a weak interaction assumption can be made wherein the airflow can affect the fuel droplet behavior but the fuel droplet behavior does not affect the airflow.

Anderson, O. L.↗
NASA NTRS1975

Study of the application of hydrogen fuel to long-range subsonic transport aircraft. Volume 1: Summary

The feasibility of using liquid hydrogen as fuel in advanced designs of long range, subsonic transport aircraft is assessed. Both passenger and cargo type aircraft are investigated. Comparisons of physical, performance, and economic parameters of the LH2 fueled designs with conventionally fueled aircraft are presented. Design studies are conducted to determine appropriate characteristics for the hydrogen related systems required on board the aircraft. These studies included consideration of material, structural, and thermodynamic requirements of the cryogenic fuel tanks and fuel systems with the structural support and thermal protection systems.

Brewer, G. D.↗